Magnetic writing materials set



May 29, 1962 c. R. TATE 3,036,388

MAGNETIC WRITING MATERIALS SET Filed Oct. 27, 1961 INVENTOR: CLARENCEFl. TATE ATTORNEY Unite States The history of writing materials beginswith the stylus and clay tablets. It has progressed through thedevelopments of art to the use of a wide variety of media, instrumentsand tools. Lithography, in which the artist works directly upon thestone was invented in the last century, as a development branching offfrom the etching plate upon which early artists worked directly withneedles or gravers.

Modern lithography received its great impetus with the invention of thehalf-tone screen, by means of which areas of colors can be reproduced ascomposites of three primary colors, each printed as a series of dots ofvarying sizes. The use of the dots and holes of modern lithography hasbeen necessary to define the resolution with which reproduction can beattained.

I have invented a set of magnetic writing materials, and a method ofWriting therewith, which is related to the reproduction of linework bymeans of dots.

The principal object of my invention is to produce a completely magneticset of Writing materials. The writing surface is composed of magneticparticles or granules, the writing instrument is composed of amagnetized tool, and the writing eraser is also composed of a magnetizedinstrument.

A further object of my invention is to produce a dustfree and clean setof writing materials, with none of the many disadvantages inherent inthe use of chalk with a blackboard, and the traditional chalk eraserwhich only serves to smear chalklines into grey smudges, while spreadinggreat amounts of chalkdust in the air.

An additional object of my invention is to produce a set of writingmaterials which will not dirty or otherwise affect the hands andclothing of the individual writer, such as is common with ink and pencilin combination with the ordinary paper.

A still further object of my invention is to provide a set of writingmaterials in which no drying fluid will form a part of the combination,in which permanence or stability of the writing is inherent in thematerials them selves.

The above and other objects of my invention will be apparent to thoseskilled in the art from a study of the accompanying drawings forming apart of this specification and illustrating in the different figuresseveral views of the particular embodiment of the invention.

In the drawings:

FIGURE 1 is a cross-section view through the writing surface, togetherwith a portion of the writing instrument involved;

FIGURE 2 is a plan view of a portion of the writing surface as itappears to the writer;

FIGURE 3 is a side view of the magnetic eraser; and

FIGURE 4 is an end view of an alternative eraser.

Referring now particularly to FIG. 1, the numeral 1 is given to theWriting surface or sheet. The surface 1 is seen to consist of a frontsurface 2 and a rear surface 3, which together form a hollow cavity,which is fluid tight. I prefer to have both the front surface 2 and therear surface 3 made of a plastic material such as plexiglas, or otheracrylics, which are either transparent or translucent, to light in thevisible wavelengths.

Front surface 2 is molded on its inner side with a series of pockets orforaminations as shown in FIG. 1. In the embodiment shown the pockets 4,4 consist of in dentations made in the form of sections of the surfaceof a sphere, all identical.

Disposed between the front surface 2 and the rear atnt surface 3 are anumber of particles. I have chosen to illustrate theseas spheresalthough they may be granules, pellets, and indeed may be irregular inform. In the preferred form these particles are spheres of a slightlysmaller diameter than the diameter of the pockets on the inner side ofthe front surface 2. The spheres are numbered 5, 5. In the preferredembodiment there are two vertical rows of these spheres, and they areposi tioned in staggered relationship. In fact I prefer to restrain themin a condition such that the distance between the inside of the frontsurface 2 and the inside of the rear surface 3 is less than two timesthe diameter of the particles. Thus the particles are not only staggeredbut crowded.

Also filling the cavity between the front surface 2 and the rear surfaceis a solution in the form of a liquid 6. In the complete writing surfaceor sheet, I prefer to have the cavity filled entirely with this solutionand to have no air bublbes.

The specific gravity of the solution 6 and the density of the particles5 is quite close, by choice, so that the particles tend to float withoutappreciable friction, either from other particles or from the innerwalls of the surfaces. As a consequence the particles 5 are free torotate in their restrained positions, that is they are free to rotatebut they cannot move translationally. Each particle is constrained toremain always next to its immediately adjacent neighbors in touchingabutment.

The particles are made by mixing an aggregateof equal parts of bariumferrite, a magnetic material of highre tentivity, and plaster of Parisor some other such filler and binder. Another possible combination isbarium ferrite together with wood flour and glue. The aggregate is inthe former case, mixed thoroughly together and then mixed with water. Itis then molded into balls or spheres and allowed to harden, whether bythe addition of heat or the passage of time. v I

The purpose of mixing equal parts of the barium ferrite with a filler isto lower the unit volumetric ma netization of the spheres below thepoint at which they will stick together with magnetization. At thispoint, I magnetize the spheres so that there is a north pole'at onepoint on the sphere surface and a south pole situated 180 degrees awayfrom the north pole, that is, on the opposite side of the sphere. I thenpaint one pole, for instance the north pole a dark color such as a blackand the opposite pole a light color or I may leave the latter unpaintedin which case it is the color of the mixture of plaster and bariumferrite, which is a chalky mixture and equivalent to white.

The outer surfaces of the spheres may be painted in two equal areas ofcolor, but I prefer to have a dominating" color. For this purpose, inthe illustration of FIG; 1, I have used white as the dominating color.This means that the white area is approximately 55% of the total area ofa given sphere, whereas the remaining color, black is allowed to coveronly 45% of the total area.

For writing on the sheet v1, I use a bar magnet in the shape of a penciland having a Writing tip between two and three times as wide as thediameter of the spheres 5, 5. The tip is numbered 7 and is magnetized inthe illustration of FIG. 1 with a south pole. The tip 7 is covered witha thin film of plastic 8.

Wrapped around the magnet, outside the plastic film is a conical shell 9made of soft iron which extends past the tip of the magnet 7. Thepurpose of this shell construction is to restrict the field of themagnet so that while the field extends beyond the tip, horizonally inFIG. 1

to influence the balls, it will not extend sidewise of the soft ironshell 9, that is, vertically in FIG. 1. This means that the field canonly affect the positions of two balls at one time.;-

The entire assembly, including the extending soft iron 1 consists of amagnet .12.

As the tip 7 of the writing instrument is brought close to the frontsurface 2, the two spheres immediately adjacent the tip 7 will rotate intheir pockets or sockets 4, 4

so that these two spheres numbered L1, 11 will present their northsides, the black sides to the right of FIG. 1, that is to the frontsurface. If the magnetized tip 7 has a strong enough field,'a ball ortwo located behind the first column will also rotate, although I havenot illustrated this in FIG. 1. a

Thus in Writing the tip 7 is merely rubbed lightly over the frontsurface 2 and a re-orientation of the spheres occurs. Whereas at'thebeginning all the spheres were aligned so that their white sides, thatis, the south poles were at the right in FIG. 1, now those spheres orparticles nearest the tip 7 have been rotated so that they areoppcsitely aligned. The result is' shown in FIG. 2, where the numeralseven is shown, written in a two column Wilde stroke in black, as itappears on a background of w ite.

In FIG. 3 I illustrate the eraser of the writing set, which The erasingmagnet is a rectangular shape. On one side, the black, 16, it ismagnetized north, whereas on the opposite side it is magnetized south,14. The entire eraser magnet is encased in a covering 15 of thin plasticwhich is soft and will not mar .or ruin the writing sheet by beingrubbed against it.

The eraser is used in the following way. The side which is magnetizednorth, :13, is laid against the front surface of the sheet 1, and thenpatted against that sheet. This action causes the south poles of thespheres, to be attracted to the north poles of the eraser. All thespheres are thus aligned with their south sides, the white ones, to theright in FIG. 1. The numeral seven of FIG. 2 has been-erased, and thespheres 11, 11 of FIG 1 have rotated to their original positions.

For a blackboard-sized sheet I prefer to use spheres or particles havinga diameter of approximately to 35 mils, that is approximately one-thirt-second of an inch. 7 Thus the tip of the writing instrument isapproximately onesixteenth of an inch wide,'and the resulting line drawnby the writing instrument is the same width as that of the writing tip.

For a portable hand toy or ordinary letter-sized writing sheet, I preferto use particles of a size between 5 and 10 mils though they can ofcourse be made smaller or larger as preferred. Smaller particles havebeen made by spraying or forcing the aggregate of barium ferrite andplaster through a spray gun so that they dry and harden before theyland, in the manner of shot dropped through a layer of heated air. Thesesmaller particles are then laid on a sheet of aluminum and passedthrough'a magnetizing field, and'painted in any of the customarymanner-s for small particles. The S mil particle results in a line 10mils wide on the Writing sheet. a

In FIG. 4 I show an end view of an alternative eraser magnet which isformed of a sheet of iron. This sheet is magnetized oppositely on itsfiat sides and then bent into the form of a cylinder. Thus an inner andouter surface is formed, 16 and 17. This cylinder magnet eraser can thenbe rolled across the writing surface to erase the writing. The northpolar surface 17 attracts the south poles of the spheres and rotates thespheresdl, 11 of FIG. 1 it their original positions. If desired, thecylinder magnet eraser can be provided with a handle, so that itresembles a rolling pin, if the handle is on the end, or it can be madelike a paint roller, in which case the handle is set perpendicular to a.wire running down the center of the cylindrical magnet.

It is possible to vary the above proportions between wide margins. Ihave used a mixture of one-third barium ferrite with two-thirds plaster.In this case it was necessary to change the density of the solution 6 inorder to keep the particles buoyant and lower their friction againsteach other. To vary the density, common table salt, in varyingproportions, may be used; it is added simply 'by dissolving in water.Many water-soluble salts can be used alternatively, and even organicsalts may be used in connection with an alcohol or other organicsolvent. As little as one-tenth barium ferrite may be used, in whichcase the magnetic forces are very weak. Again the solution may beomitted when a writing tip of relatively stronger magnetizationis'employed. The stronger magnetization will provide greater magneticforces to turn the spheres. In this case the buoyancy forces of thesolution are not required, to overcome the friction forces between theparticles.

Also it will be obvious to those practicing the invention that more thantwo vertical columns may be employed and that the dimensions of the tipwith respect to the diameter of the particles may 'be greater or lesser.Similarly the back surface may be used as the front surface, so long asit is transparent like the front surface 2. Also another possiblemodification is to leave out. the pockets and use a writing tip withrelatively stronger magnetization, which can itself overcome thefriction forces between the particles holding them in position.

Various other modifications and alterations may be made in thecombination as will be apparent to those skilled in the art. The scopeof the invention therefore should not be considered as limited to thesespecific details but is to be ascertained from the appended claims.

Iclaim:

1. A set of writing materials consisting of a writing sheet in the formof a front surface and a rear surface, a series of magnetized ballsdisposed between said front surface and said rear surface in columns,pockets formed on the inside of said front surface and one column ofsaid balls disposed in said pockets, and a friction-lessening solutionfilling the spaces between said surfaces and said balls, each ballmagnetized with a north and a south pole, .said north poles beingpainted one color and said south poles painted with a contrasting color,a writing instrument consisting of a magnet formed with a pole at onetip and a covering for said pole in the form of a plastic film, asurrounding shell of soft iron which eX- tends beyond the writing tip ofsaid magnet, and a plastic boot covering said writing tip.

2. The combination of claim 1, wherein the writing instrument isprovided with a magnetized tip approximately twice as wide as thediameter of the magnetized balls.

References Cited in the file of this patent UNITED STATES PATENTS1,074,533 Schowalter Sept. 20, 1913 1,549,197 Hanback Aug. 11, 19252,530,013 Hanback Nov. 14, 1950 2,589,601 Burnett Mar 18, 1952

